Fast pyrolysis is a thermal process during which solid biomass feedstock containing lignocellulosic material, i.e., plant and algae matter including dedicated energy crops, wood waste, and agricultural waste, is rapidly heated to pyrolysis temperatures of about 300° C. to about 900° C. in the absence of air using a pyrolysis reactor. Under these conditions, solid and gaseous pyrolysis products are formed. A vapor portion of the gaseous pyrolysis products can be condensed into biomass-derived pyrolysis oil.
Biomass-derived pyrolysis oil can serve as a potential feedstock in the production of biofuels in petroleum refineries or in stand-alone process units. In fact, biomass-derived pyrolysis oil has the potential to replace up to 60% of transportation fuels, thereby reducing the dependency on conventional petroleum and reducing its environmental impact. However, biomass-derived pyrolysis oil is a complex, highly oxygenated organic liquid having properties that currently limit its utilization as a fuel. For example, conventional biomass-derived pyrolysis oil has high acidity (with a low pH and high total acid number (TAN)) making it corrosive to storage, pipes, and downstream equipment. Conventional biomass-derived pyrolysis oil typically has a pH of less than 3 and a TAN greater than 150. Further, conventional biomass-derived pyrolysis oil has low energy density and susceptibility to increased viscosity over time. The high acidity and low energy density of the biomass-derived pyrolysis oil is attributable in large part to oxygenated hydrocarbons in the oil, particularly carboxylic acids such as formic acid, acetic acid, etc. The oxygenated hydrocarbons in the oil are derived from oxygenated hydrocarbons in the gaseous pyrolysis products produced during pyrolysis.
To convert conventional biomass-derived pyrolysis oil into usable fuel for power or heat generation, or for transportation uses, further processing is required to reduce its acidity (as measured by an increase in pH). Often, this processing results in phase instability of the biomass-derived pyrolysis oil. Also, the processing can be quite costly, including high costs for hydrogen used in acidity reduction.
Accordingly, it is desirable to provide processes for converting lignocellulosic material into pyrolysis oil having reduced acidity. It is also desirable to produce lignocellulosic-derived pyrolysis oils having reduced acid and increased energy density. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.